The present invention relates to a process for the treatment of isolated vegetable protein to provide an isolate of improved functionality and whiteness.
Vegetable protein materials such as soy protein, in their native state, contain glycinin as the major storage protein which is located in the subcellular particles called protein bodies. The glycinin is a compact, globular protein in which many of the amino acid residues are buried in the interior of the protein globules and therefore unavailable for reaction. The protein globules are held together by hydrogen bonding, hydrophobic interactions and disulfide bonding. It would be highly desirable to achieve a significant degree of reduction of the disulfide bonds of the protein to thereby dissociate or unfold the protein and prevent its reaggregation. Dissociation and reduction of the protein should provide the protein with improved properties such as better solubility, lower viscosity and other functional improvements therefore being more useful in a number of food and industrial applications.
Chemical reduction of the disulfide bonds of a vegetable protein material by a reducing agent has been employed but typically achieves minimal reduction of the disulfide bonds because many of the bonds are inaccessible to the chemical reducing agent. While the application of heat to a solution of the protein material will also assist in dissociation or unfolding of the protein particularly when employed in combination with chemical reduction of the disulfide bonds, less than 70% reduction of disulfide bonds takes place because the proteins aggregate upon the application of heat thereby preventing complete or substantial reduction of the disulfide bonds. Furthermore, the use of chemical reducing agents will many times render the protein product unsuitable for food applications. The protein contained in vegetable protein materials such as soybeans could be made more functional and useful for food applications if a means could be found for a substantial reduction of the disulfide bonds of the protein, thereby unfolding the compact structure of the protein and making it more available for other chemical reactions.
The means for reducing disulfide bonds of the protein contained in vegetable protein materials such as soybeans has been achieved in the present invention by the use of an electrolytic reduction process for conversion of the disulfide bonds contained in the protein thereby permitting the protein to unfold and dissociate from its compact form thereby providing an isolate of an improved degree of functionality for food and industrial applications. An unexpected advantage of the present process without regard to whether or not the disulfide bonds of the protein are reduced is an improved degree of whiteness of the protein material obtained following electrolytic reduction. The exact reason for this unexpected phenomenon is not completely understood but apparently electrolytic reduction also reduces the chlorogenic pigments which are apparently trapped or entrained in the native protein structure, thereby altering or eliminating these pigments which results in a protein material which has a more pronounced degree of whiteness than any protein isolate which has heretofore been available.
It is therefore an object of the present invention to provide a process for the treatment of a vegetable protein material to provide a material of improved functionality and whiteness.
It is an object of the present invention to provide a process for the treatment of a vegetable protein material to provide an isolate of improved functionality and whiteness.
It is a further object of the present invention to provide a process for the treatment of an isolated vegetable protein material, particularly soybeans, wherein the disulfide bonds of the protein material are significantly reduced thereby permitting the formation of a protein of an improved degree of functionality for food and industrial applications.
It is a still further object of the present invention to provide a process for the reduction of the disulfide bonds of a vegetable protein material that is significantly more efficient and easy to perform than those methods that have been employed in the prior art.
It is a still further object of the process of the present invention to provide a protein material which has an improved degree of whiteness over protein materials produced in the prior art.